The present invention pertains to an apparatus and method for providing on demand mixing of ink at a printer for effecting rapid clean up at the end of the print run.
In rotary offset or flexographic printing, thin films of ink are applied uniformly to the surfaces of rotating rolls, transferred to the surfaces of adjacent counterrotating rolls which may be intermediate or print rolls, and ultimately to the surface of a web of paper or other material running between a print roll and a counterrotating backing roll. In one common type of flexographic printing apparatus, the printer includes an ink transfer or anilox roll onto the surface of which a thin film of ink of metered thickness is applied in a well known manner utilizing an ink supply reservoir and a doctor blade. A chambered doctor blade is one commonly used device in which a pair of doctor blades engage the surface of the anilox roll and form the upper and lower circumferential walls of an enclosed ink supply chamber.
In conventional flexographic printing, the ink color for a print run is premixed and brought to the printer in a bucket or similar container from which it is fed to a chambered doctor blade or other device for applying ink to the anilox or ink transfer roll. The volume of ink in the bucket must be estimated based on the size of the print run and, as a result, it is common to overestimate and to have a significant amount of mixed ink remaining at the end of the run.
The clean up of ink at the end of a flexographic printing run is also a tedious and time consuming job, often requiring major adjustments and even some disassembly of the equipment. In addition to the excess volume of ink which may remain in the ink supply container, the doctor blade chamber should also be emptied prior to cleaning in order to save ink and to avoid making the clean up job even more difficult.